Various manufacture processes of semiconductors greatly depend on the substrate temperature. Therefore, the control of the substrate temperature is important in manufacturing a semiconductor, and performing a uniform temperature control on the substrate is especially important because the substrate has a certain size.
Particularly, the control of the substrate temperature is important for a Metal-Organic Chemical Vapor Deposition (MOCVD) reactor. MOCVD is an abbreviation of Metal-Organic Chemical Vapor Deposition. MOCVD is a new Vapor Phase Epitaxy growth technique developed based on the Vapor Phase Epitaxy (VPE) growth. In MOCVD, organic compounds of III family element and II family element, hydrides of V family element and VI family element, and the like are used as source material for growing a crystal, the Vapor Phase Epitaxy is performed on the base material in a manner of thermal decompose reaction, so as to grow various semiconductors of III-V family and II-VI family compounds and thin layers of single-crystal material of multi-solid solutions thereof.
In the manufacture process of MOCVD, multiple parameters, such as substrate temperature, pressure, flow speed of gas, are needed to be monitored and controlled, so as to achieve an expected epitaxial growth of a crystal. The control of the substrate temperature is particularly important, and the stability and accuracy of the substrate temperature will directly affect the effect of the manufacture process. In MOCVD, multiple substrates are usually provided on a susceptor, and the susceptor can rotate quickly and cooperate with a gas spray header provided in the upper chamber, for supplying a uniform and fast manufacture platform for batch manufacture processes. Therefore, in the manufacture process of MOCVD, the temperature is usually measured by using a non-contact measurement mechanism.
In the prior art, the temperature of the substrate is usually measured by using the principle of light reflection and transmission. FIG. 1 is a schematic diagram of a principle of measuring the temperature of a substrate in a MOCVD reactor in the prior art. An active emitting light source 101 is provided above a substrate S, for continuously emitting incident lights S11 onto the surface of the substrate S at a certain angle, and the incident light S11 is reflected by the surface of the substrate S, to obtain a reflected light S12′ expected. Further, a detector 102 is provided above the substrate S, for capturing the reflected light S12′. Further, in the prior art, related means (not shown) will also be provided for obtaining the radiant quantity of the substrate S. The following equation is used:E(λi)=T(d)×M(λi,T),
where E(λi) is the radiance emitted from the susceptor through the substrate S; M(λi,T) is blackbody radiation equation, which is a function of any wavelength λi selected from the radiance and the substrate temperature T; T(d) is the transmittance of the substrate, where T(d)=1−R, R is the reflectivity of the substrate S, which is calculated based on the incident light S11 emitted from the light source 101 and the reflected light S12′ obtained above the substrate S.
However, referring to FIG. 1, there are multiple uncertain factors during the manufacture processes of the substrate. For example, in the MOCVD reactor, a batch of substrates S to be processed is placed on the susceptor (as shown in FIG. 1). In order to obtain uniformly distributed gas on the multiple substrates and other uniform conditions for manufacture, the susceptor is required to rotate in a high speed (500-900 revolutions per minute or even 1000 revolutions per minute) under the driving of a shaft provided under the susceptor. Because high temperature (such as 1200 degree Celsius) is required during the MOCVD manufacture process, the substrates S are only placed in grooves of the susceptor. The substrates S may be sloped during the rotation due to centrifugal force generated by the high-speed rotation. Further, during the manufacture process, patterns are generated on the surface of the substrate because multiple films are grown on the substrate by epitaxy, which causes the surface of the substrate uneven. The above factors will result in that the reflected light will not be detected in the expected path. However, the detector is generally fixed at the same position. Referring to FIG. 1, in the existing temperature measurement mechanism, the substrate S is usually regarded as an object which performs mirror reflection, thus the light source 101 and the detector 102 are provided axial-symmetrically with respect to and above the substrate S, and the reflected light will expectably return in the path S12′, so that the reflected light will be exactly obtained by the detector 102. However, in fact, the reflected light will return in, for example, the path S12. Therefore, it is difficult to obtain the reflected light because the detected range of the detector 102 is limited. Therefore, the temperature measurement mechanism in the prior art will lead to big error.
Thus, a more stable and reliable temperature measurement mechanism for a substrate is needed in the field, and based on this consideration, the invention is proposed.